1. Field of the Invention
The present invention relates to cyanoacrylate compositions in non-flowable forms. More particularly, the present invention relates to non-flowable cyanoacrylate compositions which can be packaged in a convenient pocket-sized applicator dispenser for use in spreading the cyanoacrylate compositions onto substrates.
2. Brief Description of Related Technology
Cyanoacrylate adhesive compositions, particularly α-cyanoacrylate compositions, cure very rapidly and can be used on a variety of substrates. Cyanoacrylate adhesive compositions are generally applied in drops of a low-viscosity liquid composition for adhesion at particular spot locations. The liquid compositions may include a thickener to provide a composition capable of being retained to a substrate while the composition is being cured. Thickeners include acrylate resins, such as polymethyl(meth)acrylate and polymethyl(meth)acrylate, polymeric alkylcyanoacrylates, cellulose esters, such as cellulose acetate and cellulose butyrate, and polyvinyl ethers, such as polyvinylmethyl ether. See U.S. Pat. No. 3,742,018. In many applications, however, the dispensing and application of low-viscosity compositions is cumbersome.
Fumed silicas have in the past been added to cyanoacrylate compositions to render the compositions thixotropic. See U.S. Pat. Nos. 4,533,422 and Re. 32,889, and 4,837,260. The thixotropic, fumed-silica-containing cyanoacrylate compositions are described as being in the form of a nonflowable gel which will not substantially move when placed on a substrate. These cyanoacrylate compositions may also contain thickeners, such as for the purpose of preventing the fumed silica from settling in the composition. Disclosed thickeners include poly(meth)acrylates, polycyanoacrylates, and poly(vinyl)acetates.
It is well known to formulate adhesives as “stick” compositions. The patent literature on stick adhesives is extensive and covers a broad range of adhesive types, from emulsion adhesives through solvent based adhesives, to contact adhesives as well as gelling and solidifying additives for the preparation of the sticks ranging from thermosetting through natural polymers to inert fillers. An example of one such adhesive stick is sold under the trade name PrittStick™ by Henkel KGaA. This is an emulsion-based adhesive.
A number of patent documents identify adhesive compositions that have been formulated as soft-solids, and in some cases sticks. For instance, U.S. Pat. No. 5,433,775 discloses an adhesive stick consisting of a water based preparation of starch derivatives and a soap gel as the shaping gel-forming component. See also U.S. Pat. No. 5,371,131.
U.S. Pat. No. 3,846,363 relates to an adhesive crayon composition containing a sorbitol-benzaldehyde reaction product as an additive. U.S. Pat. No. 4,639,475 discloses an adhesive stick composed of the reaction product of sorbitol and/or xylitol and benzaldehyde as the gel-forming composition together with an adhesive resin which is the reaction product of methyl vinyl ether/maleic acid anhydride copolymers with partially neutralized acid phosphate esters of non-ionic wetting agents of the lower alkylene oxide adduct type. Room temperature dimensionally stable cyanoacrylate compositions have also been prepared with condensation products of aldehydes and ketones with polyols, such as dibenzylidene sorbital. See International Patent Application Nos. WO 00/32709 and WO 01/91915, and Canadian Patent Application No. CA 2353605.
Japanese unexamined patent application laid open (Kokai) 51-103939 describes a stick-like epoxy adhesive and a stick-like epoxy hardening agent which is used therewith. The sticks in JP '939 seem to be obtained by suitably compounding a gelling agent and/or water and/or organic solvent with a liquid or solution type epoxy adhesive and a epoxy hardening agent.
German Patent Document DE 199 57 677 A1 (Henkel KGaA) describes a cyanoacrylate adhesive, coating or sealing material which also contains at least one condensation product of an aldehyde or ketone with a polyol. The adhesive may be in stick form.
Adhesive compositions have also been rendered non-flowable. For example, U.S. Pat. No. 4,497,916 discloses a continuous liquid phase non-cyanoacrylate adhesive composition to which is added solid wax-like particles dispersed therein. These particles may be chosen from polyethylene glycol materials having 4,000 to 20,000 molecular weight, stearic acid, acid waxes or stearic esters. The compositions disclosed in the '916 patent are formed by heating this combination of materials in slurry form and applying it, while heated, to threads. The composition then cools to obtain a non-mobile coating. This composition requires substantial preparation in order to obtain the composition and apply it on parts. U.S. Pat. No. 3,547,851 discloses anaerobic compositions which have been rendered non-flowable through the inclusion of various waxes.
U.S. Pat. No. 6,451,927 describes a non-flowable poly(meth)acrylate adhesive composition having a polymeric matrix in sufficient quantity where it is non-flowable at temperatures up to 180° F. (82° C.) while being dispensable at room temperature without the application of heat.
U.S. Pat. No. 6,797,107 describes an adhesive composition which comprises at least one cyanoacrylate monomer and at least one solidifying polymer. The adhesive composition is reportedly capable of polymerizing to form an adhesive polymer and before such polymerizing, the adhesive composition is reported to have a liquifying point within a specified temperature greater than about 20° C. and such polymerizing is reported to not substantially occur until the adhesive composition is liquefied. The adhesive composition is reported to be in solid form at room temperature and the solidifying polymer is said to be a homopolymer of a certain structural formula, an example of which being caprolactone, such as Tone Polyol P-767-E and Tone Polymer P-767 Pellets.
Recently, Henkel Corporation introduced a line of adhesive products in the form of a stick. For instance, LOCTITE QUICK STIK 248, 268, 668, 548, 536 and PST 561 are members of that product line. However, conspicuously absent from this product line is one based on cyanoacrylates. One reason for this is that cyanoacrylates are notoriously sensitive to premature polymerization or destabilization, which is because of the cure profile or physical characteristics of the cyanoacrylate.
And more recently, Loctite (R&D) Ltd. designed a cyanoacrylate composition set forth in U.S. Patent Application Publication No. 2007/0092481, which speaks to a cyanoacrylate composition comprising a) at least one α-cyanoacrylate compound; and b) a polymer material constructed from poly(ethylene glycol) and polybutylene terephthalate) sections.
Accordingly, it would be desirable to provide a thickening agent for use as a constituent in cyanoacrylates that can be used in a variety of concentrations without adversely affecting the shelf life of the cyanoacrylate while having a dramatic impact on the viscosity, permitting the formulation of cyanoacrylates in a variety of viscosities up to and including a non-flowable form, at room temperature.
Thus, there is a need for cyanoacrylate compositions in non-flowable and gel form, such as those that can be packaged in a convenient pocket-sized applicator dispenser for use in applying and spreading the cyanoacrylate compositions onto substrates.